Quantum metrology and quantum memory using defect sates with spin-3/2 or higher half-spin multiplets

1. A method for creating a quantum memory device, including providing a sample of SiC having at least one spin-3/2 V Si − monovacancy defect therein, the V Si − monovacancy defect having a ground state (GS) and being situated in the presence of nearby nuclei; applying a first set of laser pulses to the SiC sample, the first set of laser pulses being configured to cause the V Si − defect to become spin-polarized to produce an initial population of m s =±3/2 states; applying a first static magnetic field B z along a c-axis of the SiC sample, the first magnetic field B z being configured to bring and keep the SiC sample into an avoided crossing low (ACL) quantum state, the GS of the spin polarized defect being accompanied by two nuclear spins leading to an overall state of |3/2; ; applying a first B ⊥ magnetic field pulse to the SiC sample, the first B ⊥ magnetic field pulse being orthogonal to the c-axis of the sample and being configured to bring the spin-polarized m s =±3/2 state of the V Si − defect into a superposition state [|3/2; +|−1/2; ]/√{square root over (2)}; applying a B ϕ magnetic pulse along a c-axis of the defect, the B ϕ , pulse creating the form of information that can be encoded in the electron and nuclear spin states; applying a second static magnetic field B z along a c-axis of the SiC sample, the second magnetic field B z being configured to bring the SiC sample out of the ACL quantum state and prevent further interactions between the electron and nuclear spins, thereby locking the nuclear spin polarizations into their current state where the electron information is stored and writing the information into nuclear memory.

2. The method for creating a quantum memory device according to claim 1 , further comprising applying a third magnetic field B z along a c-axis of the SiC sample, the third magnetic field being configured to bring the SiC sample into an avoided crossing high (ACM quantum state.

3. The method for creating a quantum memory device according to claim 1 , further comprising: applying a second set of laser pulses to the SiC sample, the second set of laser pulses being configured to cause the V Si − defect to become spin-polarized to produce a population of m s ±3/2 states, the first set of laser pulses further producing a first PL signal PL init that is read by a photodetector; applying a second magnetic field B z to the SiC sample, the third magnetic field B z being configured to bring the defect back into the ACL regime and redistribute the m s =+3/2 population between m s =+3/2 and m s =1/2 states determined by a phase difference ϕ; and applying a third set of laser pulses to the SiC sample, wherein the third set of laser pulses are configured to optically excite the m s =+3/2 and m s =−1/2 states in the V Si − defect and to produce a second PL signal PL out upon their relaxation to a ground state, the PL signal PL out being received by the photodetector; and converting a difference (PL out −PL init ) between the first and second P signals into the information stored in the memory.